/**
     * 流式查詢(xún),全量導(dǎo)出
     *
     * @param req  查詢(xún)條件
     * @param size 單個(gè)文件數(shù)據(jù)最大條數(shù)
     * @return
     */
    @ApiOperation(value = "流式查詢(xún),全量導(dǎo)出")
    @GetMapping("/streamAll")
    public BaseResultModel streamAll(ReqBillRecordBackQuery req, Integer size) {
        try {
            billRecordBackService.streamAll(req, size);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
        return BaseResultModel.success();
    }

 @Override
    @Transactional
    public void streamAll(ReqBillRecordBackQuery req, Integer size) throws Exception {
        exportXml(req,size);
    }
    private void exportXml(ReqBillRecordBackQuery req, Integer size) throws Exception{
        //文件內(nèi)容行數(shù)
        Integer in = 0;
        //文件名稱(chēng)
        Integer fileName=0;
        String name = "exportTest";
        String suf =".txt";
        String path = "H:\\新建文件夾\\新建文件夾\\export\\";
        File ff = new File(path);
        //遞歸刪除目錄中的所有文件和子目錄，而不刪除目錄本身。
        FileUtils.cleanDirectory(ff);
        File fe = new File(path+name+fileName+suf);
        //刪除此抽象路徑名表示的文件或目錄
        //mkdirs()可以建立多級(jí)文件夾， mkdir()只會(huì)建立一級(jí)的文件夾
//        fe.mkdirs();
        //獲取文件輸出列
        BufferedWriter bufferedWriter=new BufferedWriter(new FileWriter(fe));
        StringBuilder sb = new StringBuilder();
        Cursor<BillRecordBack> billRecordBacks = mapper.streamAll(req);
        for (BillRecordBack bil : billRecordBacks) {
            sb.append(bil).append("\n");
            in++;
            if (in>=size){
                in=0;
                fileName++;
                fe = new File(path+name+fileName+suf);
                bufferedWriter = new BufferedWriter(new FileWriter(fe));
            }
            bufferedWriter.write(sb.toString());
            //將StringBuilder數(shù)據(jù)重置
            sb.setLength(0);
        }
        //最后需要自己關(guān)閉流
        billRecordBacks.close();
        bufferedWriter.close();
    }

    <select id="streamAll" resultType="com.psh.hik.entity.BillRecordBack" fetchSize="5000">
        select t_id,r_id,r_time,r_number,descd,deleted,ctime,crname,mtime,chname from  bill_record_back
        <where>
            <if test="null != param.rTime and ''!= param.rTime">
              ctime = #{param.rTime}
            </if>
            <if test="null != param.rNumber and ''!= param.rNumber">
                ctime = #{param.rNumber}
            </if>
        </where>
    </select>

    private void exportNote(ReqBillRecordBackQuery req, Integer size) throws Exception{
        //lambda表達(dá)式訪問(wèn)外部變量有一個(gè)非常重要的限制：變量不可變（只是引用不可變，而不是真正的不可變）,AtomicInteger是一個(gè)提供原子操作的Integer類(lèi)，通過(guò)線程安全的方式操作加減。
        //文件內(nèi)容行數(shù)
        AtomicInteger in = new AtomicInteger(1);
        //文件名稱(chēng)
        AtomicInteger fileName= new AtomicInteger(0);
        String name = "exportTest";
        String suf =".txt";
        String path = "H:\\新建文件夾\\新建文件夾\\export\\";
        File ff = new File(path);
        //遞歸刪除目錄中的所有文件和子目錄，而不刪除目錄本身。
        FileUtils.cleanDirectory(ff);
        AtomicReference<File> fe = new AtomicReference<>(new File(path + name + fileName + suf));
        AtomicReference<BufferedWriter> bufferedWriter= new AtomicReference<>(new BufferedWriter(new FileWriter(fe.get())));
        StringBuilder sb = new StringBuilder();
        mapper.exportNote(req,resultContext -> {
            try {
                if (fileName.get()>=20){
                    return;
                }
                BillRecordBack resultObject = resultContext.getResultObject();
                sb.append(resultObject).append("\n");
                //a.incrementAndGet(); 先+1，再返回,a.getAndIncrement()先返回，再 +1
                in.getAndIncrement();
                System.out.println(in);
                if (in.get() >=size){
                    in.set(0);
                    fileName.getAndIncrement();
                    fe.set(new File(path + name + fileName + suf));
                    bufferedWriter.set(new BufferedWriter(new FileWriter(fe.get())));
                }
                bufferedWriter.get().write(sb.toString());
                //將StringBuilder數(shù)據(jù)重置
                sb.setLength(0);
            }catch (Exception e){
                throw new RuntimeException(e);
            }
        });
        bufferedWriter.get().close();
    }

    @Select("select t_id,r_id,r_time,r_number,descd,deleted,ctime,crname,mtime,chname from  bill_record_back")
    //這個(gè)注解是設(shè)定每次流式查詢(xún)的iterator大小的，這里是1000條 ,ResultSetType.FORWARD_ONLY 只允許游標(biāo)向下移動(dòng)
    @Options(resultSetType = ResultSetType.FORWARD_ONLY, fetchSize = 5000)
    @ResultType(BillRecordBack.class)
    void exportNote(ReqBillRecordBackQuery req, ResultHandler<BillRecordBack> handler);

<dependency>
? <groupId>org.mybatis.spring.boot</groupId>
? <artifactId>mybatis-spring-boot-starter</artifactId>
? <version>1.1.1</version>
</dependency>

<select id="selectGxids" resultType="java.lang.String" fetchSize="1000">
? ?SELECT gxid from t_gxid
?</select>

package flowselect;
import org.apache.ibatis.session.ResultContext;
import org.apache.ibatis.session.ResultHandler;
import java.util.Set;
public class GxidResultHandler implements ResultHandler<String> {
? // 這是每批處理的大小
? private final static int BATCH_SIZE = 1000;
? private int size;
? // 存儲(chǔ)每批數(shù)據(jù)的臨時(shí)容器
? private Set<String> gxids;
? public void handleResult(ResultContext<? extends String> resultContext) {
? ? // 這里獲取流式查詢(xún)每次返回的單條結(jié)果
? ? String gxid = resultContext.getResultObject();
? ? // 你可以看自己的項(xiàng)目需要分批進(jìn)行處理或者單個(gè)處理，這里以分批處理為例
? ? gxids.add(gxid);
? ? size++;
? ? if (size == BATCH_SIZE) {
? ? ? handle();
? ? }
? }
? private void handle() {
? ? try {
? ? ? // 在這里可以對(duì)你獲取到的批量結(jié)果數(shù)據(jù)進(jìn)行需要的業(yè)務(wù)處理
? ? } finally {
? ? ? // 處理完每批數(shù)據(jù)后后將臨時(shí)清空
? ? ? size = 0;
? ? ? gxids.clear();
? ? }
? }
? // 這個(gè)方法給外面調(diào)用，用來(lái)完成最后一批數(shù)據(jù)處理
? public void end(){
? ? handle();// 處理最后一批不到BATCH_SIZE的數(shù)據(jù)
? }
}

package flowselect;
import org.mybatis.spring.SqlSessionTemplate;
import org.springframework.beans.factory.annotation.Autowired;
@Service
public class ServiceImpl implements Service {
? @Autowired
? SqlSessionTemplate sqlSessionTemplate;
? public void method(){
? ? GxidResultHandler gxidResultHandler = new GxidResultHandler();
? ? sqlSessionTemplate.select("flowselect.Mapper.selectGxids", gxidResultHandler);
? ? gxidResultHandler.end();
? }
}